Functional analysis of the chicken PPARγ gene 5'-flanking region and C/EBPα-mediated gene regulation.
ABSTRACT Peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer binding protein-α (C/EBPα) are the master regulators of adipogenesis. The regulatory mechanism of PPARγ and C/EBPα gene expression is clear in mammals, however, little is known in chicken. The aim of the present study was to characterize chicken PPARγ promoter and investigate whether PPARγ could be regulated by C/EBPα in chickens. A 2-kb nucleotide sequence upstream of the start codon of chicken PPARγ gene was cloned and characterized by using bioinformatics and experimental approaches. This 2-kb promoter region exhibited strong promoter activity in DF1 cells. The reporter gene assay showed that the chicken C/EBPα could activate PPARγ gene promoter. Further study by electrophoretic mobility shift assay and mutational analysis revealed that the chicken C/EBPα could directly bind to and regulate the PPARγ gene promoter. Our results demonstrate that PPARγ can be directly regulated by C/EBPα in chickens.
- SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: While an understanding of lipid metabolism in chickens is critical for a further improvement of food production, there are few studies concerning differences in lipid metabolism mechanisms between chickens and other species at a molecular level. Chickens have three PPAR gene subtypes (α, β, and γ) that function differently from those present in humans and mice. The chicken PPAR-gamma (cPPARγ) gene is shorter than that in humans and lacks a γ2 isoform. Moreover, in serum-free media, cPPARγ shows high transcriptional activity without exogenous ligands. Luciferase reporter assays were used to examine the effect of sera on cPPAR transcriptional activities and showed that adult bovine serum and chicken serum highly activate cPPARα and β functions. Moreover, we found that bezafibrate induces the transactivation function of cPPARβ, but not human PPARδ (human PPARβ ortholog). This ligand selectivity relies on one amino acid residue (chicken: Val419, human: Met444). These results show the possibilities for unique functions of cPPARs on chicken-specific lipid glucose metabolism. As such, a better understanding of the molecular mechanisms of lipid metabolism in chickens could result in higher productivity for the poultry industry.PPAR Research 01/2013; 2013:186312. · 2.69 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Folate, an essential vitamin participating in 1-carbon metabolism leading to a methyl donor function, is a key factor inducing epigenetic changes. This study sought to determine if folate influences the methylation level of cytosine-guanine (CpG) islands in the promoters of critical adipogenic genes in chickens, and how this might affect gene expression and differentiation of preadipocytes in vitro. Preadipocytes were treated with 0 to 16 mg/L of folate during the induction of differentiation, and cell proliferation and lipid accumulation were assessed. The folate supplementation resulted in enhanced cell proliferation and decreased content of lipid per adipocyte at d 6 of differentiation. The effects of folate on relative expression of genes critical for adipocyte differentiation and 1-carbon metabolism were measured by quantitative reverse-transcription PCR. Folate caused a dose-dependent decrease in transcript abundance of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα) gene expression, and the downstream enzyme fatty acid synthase; in contrast, expression of DNA (cytosine-5)-methyltransferase and methylenetetrahydrofolate reductase was obviously upregulated at d 6 of differentiation (P < 0.05). The DNA methylation was examined with the bisulfite sequencing PCR method. Overall CpG methylation in the C/EBPα gene promoter region was 21.8% lower (P < 0.05) and the gene's expression was 2.7-fold higher in the absence of folate, compared with cells treated with 16 mg/L of folate, whereas methylation of the PPARγ promoter was not affected. Overall, the results show that folate increased the proliferation of adipocytes but reduced per-cell lipid accumulation, thereby influencing differentiation; it increased expression of genes involved in 1-carbon metabolism resulting in greater methylation of the C/EBPα promoter during differentiation and decreased that gene's expression, perhaps accounting for decreased expression of PPARγ.Poultry science. 07/2014;
- [Show abstract] [Hide abstract]
ABSTRACT: Adipogenesis is controlled by a complicated process involving certain transcriptional events. In chicken adipogenesis, peroxisome proliferator-activated receptor γ (PPARγ) is a key regulator of preadipocyte differentiation and abdominal fat accumulation. However, in a recent study in mammals, some novel factors related to regulation of adipogenesis, including preadipocyte differentiation, were identified in mammals. Therefore, in this study, we aimed to determine the expression profiles of these mammalian adipogenesis-related factors, such as zinc-finger protein 423 (ZNF423), Krüppel-like factor -2, -5, and -15 (KLF-2, -5, -15), and FGF10, in the chicken (Gallus gallus). Specifically, we analyzed their expression in primary preadipocyte differentiation in vitro and also analyzed their tissue distribution and their temporal expression in adipose tissue development in vivo. During chicken adipocyte differentiation, the gene expression of ZNF423, KLF-2, KLF-5 and FGF10 was found to rapidly decrease in the early stage of preadipocyte differentiation. Expression of ZNF423 then increased in the late stage of differentiation. KLF-15 expression increased in a time-dependent manner for 48 hours. Protein expressions of these factors were reflected by western blot analysis. High levels of aP2, PPARγ and FGF10 mRNA were found in adipose tissue. In addition, aP2, PPARγ and ZNF423 mRNA levels in the adipose tissue were elevated at day 10 and 20. These expression profiles of the adipogenesis-related factors in chicken are, in part, different from in mammalian adipogenesis but this seems to reflect the differences in regulation of adipogenesis and in adipose tissue functions between avians and mammals.Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 04/2013; · 1.61 Impact Factor